Results are presented of a study of a full-scale, four-story reinforced concrete structure that was damaged by forced vibration and repaired by the epoxy-injection method. The structure was retested with low-amplitude vibrations, followed by forced vibrations. The damage to the epoxy-repaired structure was similar to that sustained by the original structure but the damage was less severe and the cracking was more widely distributed. Findings reveal that, for low-amplitude motions, the epoxy-repaired structure was slightly less stiff than the original undamaged structure. As the amplitude of the structure's response increased, the difference between the epoxy-repaired structure and the original structure decreased. At large deflections associated with severe damage, the epoxy-repaired structure was stiffer than the original structure.